Combustion chamber having a ceramic heat shield and seal

ABSTRACT

A combustion chamber of a gas turbine having a peripheral support structure and a heat shield arranged therein. The support structure has a reduced cross-section on the downstream side and a stop element on the upstream side. There is a gap between the heat shield and the stop element to compensate for different strains and tolerances. For reduction of the cooling air consumption, a peripheral sealing groove which is open towards the heat shield and has a sealing element arranged therein is provided in the stop element, which sealing element rests against the heat shield and covers the gap.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2020/085430 filed Dec. 10, 2020, and claims the benefit thereof. The International Application claims the benefit of German Application No. DE 10 2020 203 017.0 filed Mar. 10, 2020. All of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The invention relates to a gas turbine combustion chamber which has a ceramic heat shield and in the case of which a gap is sealed by means of a seal.

BACKGROUND OF INVENTION

In the prior art, various types of construction of combustion chambers are employed in gas turbines. In all cases, the high temperatures in the combustion chamber constitute the primary loading for the combustion chamber. In order to be able to realize the highest possible temperatures in the combustion chamber, a heat shield is usually inserted in the combustion chamber. To this end, the combustion chamber firstly has a support structure which is produced from a metallic material. The heat shield is arranged on the inner side of the support structure and is generally composed of a ceramic material. An exemplary embodiment in this respect is known from WO 2019/115129 A1. On the one hand, the ceramic heat shield has a considerably higher temperature resistance than the support structure. On the other hand, the ceramic heat shield serves as insulation between the combustion chamber and the support structure.

A known disadvantage is that, compared with the support structure, the ceramic material of the heat shield has a much greater sensitivity to vibrations or other mechanical loads. It is therefore generally necessary for the heat shield to be installed in as stress-free a manner as possible. This generally leads to the presence of gaps both between individual parts of the heat shield and in particular between the heat shield and adjoining components.

In order to prevent thermal damage to the support structure in the region of gaps, it is customary in the prior art to provide a cooling air flow which prevents hot gas from entering the gap.

A disadvantage in this case is, in turn, the cooling air flow, which in this respect cannot be supplied to the burner for combustion, and thus the efficiency deteriorates.

SUMMARY OF INVENTION

It is therefore an object of the present invention to propose a possibility for the reduction of the cooling air flow.

The object addressed is achieved by means of an embodiment of a combustion chamber according to the invention according to the teaching of the independent claim.

Advantageous embodiments are the subject matter of the dependent claims.

The generic combustion chamber can be provided for different uses, this embodiment being suitable in particular in the case of a gas turbine. The combustion chamber defines a combustion chamber axis which is arranged approximately centrally and which extends from an upstream side to a downstream side. The combustion chamber has a support structure which peripherally surrounds the combustion chamber axis. In this case, the support structure is at least predominantly composed of a metallic material. Apart from coatings or attachments, the support structure is advantageously composed of a metallic material. In this case, the support structure has a cross-sectional reduction on the downstream side. The manner in which the cross-sectional reduction is embodied is initially irrelevant. The support structure forms a stop element on the opposite, upstream side. Likewise, the embodiment of the stop element is initially irrelevant.

Located within the support structure, on the side facing a combustion space, is a heat shield which—apart from possible fastening means and/or coatings and/or inner reinforcements—is composed of a ceramic material. Provision is made in this case for the position of the heat shield within the support structure to be delimited, along the combustion chamber axis, by the cross-sectional reduction on the downstream side and by the stop element on the upstream side. In order to avoid impermissible clamping of the heat shield in the direction of the combustion chamber axis between the cross-sectional reduction and the stop element, provision is furthermore made for there to be a gap at least between the heat shield and the stop element.

In order to reduce the consumption of cooling air, provision is made according to the invention for a seal groove which runs around the combustion chamber axis and which is open toward the heat shield to be present in the stop element. A sealing element is arranged in the seal groove, said sealing element extending out of the stop element and covering the gap, and bearing against the heat shield.

The use of a sealing element on the upstream side of the heat shield makes it possible to reduce the consumption of cooling air and thus increase the efficiency.

The construction of the combustion chamber proves to be particularly advantageous if the support structure and consequently the heat shield have a tubular (not necessarily circular) design.

In order to ensure abutment of the sealing element against the heat shield, provision is advantageously made for at least one spring element to be present in the stop element, said spring element being elastically preloaded in the assembled state and acting in the direction of the combustion chamber axis on the sealing element, and thus the reliable abutment of the sealing element against the heat shield is ensured.

It is particularly advantageous in this case to use a spring element which is likewise arranged in the seal groove, between the groove bottom and the sealing element. The spring element may have a wave-like design, for example.

The cross-sectional reduction, on the one hand for modeling the desired cross section of the combustion chamber in the downstream region, and on the other hand for delimiting a displacement of the heat shield along the combustion chamber axis, may be modeled in different ways.

In this case, provision is made in a particularly advantageous embodiment for the cross-sectional reduction to be formed by a conical portion. In this context, the conical shaping does not necessarily necessitate a rotationally shaped design, rather similar shapes that become smaller in cross section in the downstream direction are also encompassed. In the case of a, for example, rotationally shaped design, this leads to a reduction of the diameter in the flow direction of the hot gas in the combustion chamber. Advantageously, provision is at least made in the embodiment for the heat shield to be supported, via a portion of the outer periphery of the heat shield, directly (an outer surface of the heat shield bears against the support structure) or particularly advantageously indirectly on the cross-sectional reduction. In this case, in order to avoid wear and to ensure a centric position of the heat shield within the support structure, provision may advantageously be made for at least one wear protection element and/or elastic tensioning elements, for example leaf springs, to be arranged between the outer periphery of the heat shield and the support structure.

By contrast, provision is made in an alternative embodiment for the cross-sectional reduction to comprise a shoulder. In this case, provision is made for an edge portion of the heat shield to bear directly or indirectly against the shoulder. In this case, surfaces of the shoulder and of the adjacent edge portion that bear against one another are oriented approximately perpendicularly with respect to the combustion chamber axis. An advantage in this case is the defined support in the direction of the combustion chamber axis, with the disadvantage of the possibly more complex construction of the support structure and the heat shield. In this case, it is irrelevant whether the cross-sectional reduction furthermore has a conical design.

In the simplest case, the heat shield can be formed by a single heat shield element. Advantageously, the heat shield is formed, in the direction of the combustion chamber axis, by at least two heat shield elements. In this case, provision is particularly advantageously made for the at least two successive heat shield elements to bear against one another directly or indirectly (for example by way of intermediate wear protection means).

Furthermore, it is advantageous if, in the case of a greater diameter, the heat shield is formed, in the peripheral direction, by at least two heat shield elements. Here, too, provision is advantageously made for said heat shield elements to bear against one another directly or indirectly.

In order to secure a centric position of the heat shield in the support structure, provision is advantageously made for at least one radially acting tensioning element to be present between the heat shield and the support structure. In this case, use is advantageously made of a plurality of tensioning elements which are arranged distributed over the periphery and which together bring about the centric positioning of the heat shield. In this way, tolerance compensation and compensation of thermal expansion is ensured. Preference is given to using leaf springs as tensioning elements.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment for a combustion chamber according to the invention is sketched in the subsequent figure.

DETAILED DESCRIPTION OF INVENTION

The combustion chamber 01 defines a combustion chamber axis and in this case first of all comprises a rotationally shaped support structure 02. Said support structure 02 has a cross-sectional reduction 03 with a conical design on the downstream side. Located opposite on the upstream side is a stop element 04 in the form of a shoulder.

Within the support structure 02, the heat shield 11 is in this example formed by three heat shield elements 12, 13. The downstream heat shield element 12 has a conical design, just like the cross-sectional reduction 03. In this example, the outer periphery of the heat shield element 12 bears against the inner side of the cross-sectional reduction 03. However, it is more advantageous if tensioning elements are present between the heat shield 11 and the support structure 02 in the region of the cross-sectional reduction 03. Direct abutment of the heat shield element 12 against the support structure 02 is thus avoided, and the centric position is simultaneously ensured even in the case of small differences in shape between the heat shield 12 and the support structure 02. In any case, the position of the heat shield 11 is thus delimited in the downstream direction. Adjacent thereto on the upstream side, the heat shield 11 is formed by two heat shield elements 13 which are divided in the peripheral direction. In order to ensure a centric position, provision is in this case made for a plurality of radially acting tensioning elements 14 to be arranged, so as to be distributed over the periphery, between the heat shield elements 13 and the support structure 02.

Furthermore, it is possible to see the arrangement of a seal groove 05 with the sealing element 06 arranged therein. In this case, the sealing element 06 bears against the heat shield element 13 and covers a gap between the heat shield 11 and the stop 04. Unnecessary consumption of cooling air is thus avoided. In order to ensure the abutment of the sealing element 06 against the heat shield 11, provision is furthermore made of an elastically preloaded spring element 07, said spring element 07 being arranged in the seal groove 05, between the groove bottom and the sealing element 06. 

1. A combustion chamber comprising: a combustion chamber axis, having a peripheral support structure, said peripheral support structure having a cross-sectional reduction on the a downstream side and a stop element on an upstream side, at least one ceramic heat shield, said ceramic heat shield being arranged within the peripheral support structure, on the a side facing the a combustion space, and a position of said ceramic heat shield being delimited in a direction of the combustion chamber axis by the cross-sectional reduction and the stop element, there being a gap between the ceramic heat shield and the stop element, a peripheral seal groove which is open toward the ceramic heat shield and is arranged in the stop element, and a sealing element, which bears against the ceramic heat shield and which covers the gap and is arranged in said peripheral seal groove, and an elastically preloaded spring element, which acts on the sealing element and is arranged in the stop element.
 2. The combustion chamber as claimed in claim 1, wherein the peripheral support structure has a tubular design.
 3. The combustion chamber as claimed in claim 1, wherein the elastically preloaded spring element is arranged in the peripheral seal groove, between a groove bottom and the sealing element.
 4. The combustion chamber as claimed in claim 1 of claims 1, wherein the cross-sectional reduction is formed by a conical portion, an outer periphery of the ceramic heat shield being supported directly or indirectly on said cross-sectional reduction.
 5. The combustion chamber as claimed in claim 1, wherein the ceramic heat shield is formed, in the direction of the combustion chamber axis, by at least two heat shield elements.
 6. The combustion chamber as claimed in claim 1, wherein at least one heat shield element has a tubular design.
 7. The combustion chamber as claimed in claim 1, wherein, at least in certain portions along the combustion chamber axis, the ceramic heat shield is formed, in a peripheral direction, by at least two heat shield elements.
 8. The combustion chamber as claimed in claim lone of claims 1, wherein at least one radially acting tensioning element is arranged between the ceramic heat shield and the peripheral support structure.
 9. The combustion chamber as claimed in claim 1, wherein the combustion chamber comprises a gas turbine combustion chamber. 